Force applicator

ABSTRACT

A force applicator comprises a ram operable by fluid under pressure. A pressure pad (7) is located between one movable part of the ram (3) and the load (9) and means are provided which enable relative movement to take place between the pressure pad and the ram in a direction at right angles to the direction of operation of the ram. The means may take the form of a fluid chamber (15) between the pressure pad and the ram or a disc of PTFE between them.

Rams operable by fluid pressure are employed in many industrialapplications in order to apply a force, usually between a rigidfoundation and a load plate. The ram consists basically of a pistondisplaceable in a cylinder with a part projecting from one end of thecylinder and, in use, either the cylinder bears against a rigidfoundation and the piston is displaced to apply force to the load plate,or the piston bears against the rigid foundation and the cylinder isdisplaceable to apply a force against the load plate. In someapplications it is desirable to slide the load plate relative to thepart of the ram against which it abuts. This is usually impossible toattain once pressure has been applied to the ram.

According to the present invention, a force applicator comprises a ramhaving a cylinder, a piston displaceable in the cylinder with a partprojecting from one end of the cylinder, and means for introducing fluidunder pressure into the cylinder to displace the piston; and a pressurepad abutting against either the end wall of the cylinder opposite theend from which the part projects or the end wall of the part projectingfrom the cylinder, said pressure pad being slideable with respect to thesurface against which it abuts in a direction normal to the direction ofmovement of the piston, and is characterised in that between thepressure pad and the wall against which it abuts there is a spacedefined by a recess in the pressure pad or wall and means are providedfor introducing fluid under pressure into said space.

The force required to bring about relative movement between the ram andthe pressure pad is conveniently less than 10% of the applied load.

In order that the invention may be more readily understood, it will nowbe described, by way of example only, with reference to the accompanyingdrawings, in which:

FIG. 1 shows diagrammatically the force applicator applied to a part ofa rolling mill; and

FIG. 2 shows an alternative embodiment of the invention applied to arolling mill.

Referring to FIG. 1, a hydraulically operable ram comprises a piston 1displaceable in a cylinder 3 and having a part which projects out of thecylinder. To displace the piston, fluid is introduced into the cylinderchamber 5 by means (not shown). An outer wall surface 16 of the cylinder3 extends transverse to the direction of relative movement between thepiston and the cylinder and a pressure pad 7 bears against this surface.The opposite surface of the pressure pad bears against a load plate 9which forms a chock for rotatably supporting one end of the roll of arolling mill. The pressure pad 7 is centred relative to the cylinder 3by actuating means such as springs 11 or hydraulic means within anannular bracket 13 on the underside of the cylinder 3.

The surface of the pad 7 which is adjacent the surface 16 of thecylinder is recessed over its central portion and the space 15 definedby the walls of the recess and the surface 16 of the cylinder is incommunication with the chamber 5 by way of a bore 17 extending throughthe wall of the cylinder. Alternatively, the surface of the pad may beflat with the surface 16 of the cylinder having a recess therein.

In use, the force applicator is positioned between the load plate 9 anda rigid foundation 19 and fluid is introduced into the chamber 5 of theram in order to apply a load between the foundation and the load plate9. The area of the space 15 between the pressure pad and the cylinder isapproximately 80% of the area of the chamber 5 and, if the same fluidpressure exists in the chamber 5 and the space 15, the force between thepressure pad and the cylinder is considerably reduced and, by suitableselection and lubrication of the sliding surfaces, a coefficient offriction of about 0.2 between them can be achieved. This means that theside force required on the pressure pad 7 to displace it transverse tothe line of action of the load exerted by the ram is approximately 4% ofthis load. A limited transverse movement of the pressure pad 7 is causedby movement of the load plate 9 transverse to the line of action of theforce applied by the ram.

In the arrangement shown in FIG. 2, the cylinder 21 of the ram defines achamber 22 in which the piston 23 is displaceable. The ram is mounted ona rigid foundation 25 and a pressure pad 27 is located between the outersurface 28 of the piston and a load plate 29 which may constitute achock for rotatably mounting one end of the roll of a rolling mill. Theupper surface 28 of the piston is of concave spherical form and theadjacent surface of the pressure pad 27 is of corresponding convex form.A recess 30 is formed in the upper surface of the piston and this recessis in communication with the chamber 22 of the cylinder by a bore 31extending through the piston. Again, the area of the recess 30 isconveniently 80% of the area of the chamber 22 and the sideways forcerequired to bring about tilting of the pressure pad 27 with respect tothe piston 23 is approximately 4% of the load applied by the ram betweenthe rigid foundation 25 and the load plate 29. In an alternativearrangement the space 15 or recess 30 is not in communication with theinterior of the cylinder but is connected to a separate external sourceof fluid under pressure.

In the arrangements described above, the direction of movement of thepiston or cylinder has been generally vertical but the free applicatorcan be used so that the direction of movement of the piston/cylinder isgenerally horizontal. An application for such an arrangement is the useof the applicator to control the vertical edger rolls of a rolling mill.

We claim:
 1. A force applicator comprising:a ram having a cylinder witha pair of opposite end walls, a piston displaceable in the cylinder witha part of the piston projecting from the cylinder through one of saidend walls, a separate pad retained in abutting relation with the otherend wall of the cylinder but slidable with respect to the wall againstwhich it abuts in a direction normal to the direction of movement of thepiston, the pad and said end wall against which it abuts togetherdefining a recess, means for introducing fluid under pressure into therecess, and means for introducing fluid under pressure into the cylinderto displace the piston whereby force can be applied between the surfacesengageable with the piston and the pad respectively.
 2. A forceapplicator as claimed in claim 1 wherein the recess and the inside ofthe cylinder are in communication with each other by way of a boreextending through said other end of the cylinder against which the padabuts.
 3. A force applicator as claimed in claim 1 wherein the pad isretained against the end wall of the cylinder by means includingactuating means which cause the pad to take up a predetermined positionrelative to the end wall when no load is applied to the pad by theaction of the ram.
 4. A force applicator comprising;a ram having acylinder with a pair of opposite end walls, a piston displaceable in thecylinder with a part of the piston projecting through one of the endwalls, separate pad retained in abutting relation with the end wall ofthe part of the piston projecting from the cylinder and slidable withrespect to the wall against which it abuts in a direction normal to thedirection of movement of the piston, the pad and the wall of the pistonagainst which it abuts together defining a recess, means for introducingfluid under pressure into the recess and means for introducing fluidunder pressure into the cylinder to displace the piston whereby forcecan be applied between surfaces engageable with the pad and the other ofthe ends walls of the cylinder respectively.
 5. A force applicator asclaimed in claim 4 wherein the recess and the inside of the cylinder arein communication with each other by way of a bore extending through thepiston.
 6. A force applicator as claimed in claim 5 wherein the abuttingsurfaces of the pad and the piston are of corresponding arcuate form.